Lateral asymmetry of H-reflex recovery curves in cat: evidence for a spinal motor asymmetry.

Recovery curve of the Hoffmann reflex from the left and right sides was studied in lightly anesthetized cats before and after spinalization. According to the differences in the H-reflex recovery curves from the left and right lateral gastrocnemiussoleus nerves, three populations of intact animals were found: right dominant with higher recovery curve on the right side (31.8%), left dominant with higher recovery curve on the left side (36.4%), and ambilateral with no dominance (31.8%). After spinalization the dominance remained the same in the two first groups and dominance appeared in 5 out of the 7 cats of the last group. These results provide evidence for a bilateral asymmetry of alpha motoneuron excitability in cats, which can be used as a model to study the possible mechanisms of spinal motor asymmetry.